Year	Years
1970	0.34
1971	0.35
1972	0.36
1973	0.38
1974	0.39
1975	0.41
1976	0.42
1977	0.44
1978	0.46
1979	0.47
1980	0.49
1981	0.51
1982	0.53
1983	0.56
1984	0.58
1985	0.6
1986	0.63
1987	0.66
1988	0.68
1989	0.71
1990	0.74
1991	0.78
1992	0.81
1993	0.85
1994	0.88
1995	0.92
1996	0.96
1997	1
1998	1.04
1999	1.08
2000	1.12
2001	1.16
2002	1.21
2003	1.25
2004	1.3
2005	1.35
2006	1.39
2007	1.44
2008	1.49
2009	1.55
2010	1.6
2011	1.65
2012	1.71
2013	1.77
2014	1.82
2015	1.89